A lathe is the most used machine tool among machine tools for mechanically machining a workpiece. The lathe may classified into a general lathe (a manual lathe) being manually operated, and a numerically-controlled lathe and a computerized numerically-controlled lathe being automatically operated.
Particularly, a computerized numerical-controlled lathe called a CNC lathe is a machine tool where a controller is mounted to the general lathe. The computerized numerically-controlled lathe can automatically perform a machining of various components according to a program.
The computerized numerically-controlled lathe includes a controller that is an electronic device being able to automatically operate an apparatus and an apparatus body that is a mechanical device. The controller controls an operation of the apparatus body by a CNC (computer numerical control) system program, a PLC (programmable logic control) program, and so on. The apparatus body includes a head stock, a chuck, a tool post, a tail stock, a bed, a carriage, a feed gear (a transfer saddle), a hydraulic device, like the general lathe.
In this instance, a chuck for the lathe is mounted at an end of a main spindle and grips a workpiece. The chuck may be a general chuck, a pneumatic chuck, a hydraulic chuck, a collet chuck, a magnetic chuck, and so on. Generally, the chuck grips the workpiece by interlocked movements of three or four jaws.
On the other hand, the chuck may be mostly manufactured from alloy steel for machining structural use or carbon steel for machine structure use. However, the alloy steel for machining structural use or the carbon steel for machine structure use has a specific gravity of about 7.77. Thus, the material of the alloy steel for machining structural use or the carbon steel for machine structure use is heavy, a volume of an apparatus (a machine tool) for the same is large, and power consumption increases. Thus, machining process using the chuck is inefficient.
In addition, inertia load applied to a motor of the apparatus is large when the chuck includes the heavy material, especially in high speed machining. Thus, it is hard to be used for a long time.